What Is Radiology?

Radiology is the medical discipline concerned with the use of imaging technologies and ionizing radiation to diagnose and treat disease. It encompasses the acquisition, interpretation, and application of images produced by X-rays, computed tomography, magnetic resonance imaging, ultrasound, and nuclear medicine techniques. Physicians who practice radiology, known as radiologists, provide diagnostic interpretations read from images, guide minimally invasive therapeutic procedures, and apply therapeutic radiation to treat malignancies. The field occupies a central position in modern medicine because nearly every clinical specialty relies on radiological imaging at some stage of patient care.

Radiology draws its foundations from physics, engineering, anatomy, and physiology. The clinical specialty emerged from Wilhelm Röntgen's 1895 discovery of X-rays, expanded to include fluoroscopy, ultrasound, and nuclear medicine through the mid-twentieth century, and expanded rapidly with the introduction of computed tomography (CT) in the 1970s and magnetic resonance imaging (MRI) in the 1980s. Today the field is further shaped by artificial intelligence tools that assist image interpretation and workflow management.

Diagnostic Radiology

Diagnostic radiology encompasses the interpretation of medical images to detect, characterize, and monitor disease. The primary imaging modalities include radiography for skeletal and chest assessment, CT for cross-sectional anatomy and trauma evaluation, MRI for soft-tissue contrast without ionizing radiation, and ultrasound for real-time abdominal and vascular imaging. As the IAEA's diagnostic radiology physics resources note, CT alone accounts for approximately 62 percent of the collective radiation dose from man-made sources to the global population, underscoring both its diagnostic prevalence and the importance of dose optimization. Subspecialties within diagnostic radiology include neuroradiology, musculoskeletal radiology, pediatric radiology, and nuclear radiology, each requiring focused expertise in anatomy, pathology, and the characteristics of specific imaging modalities.

Interventional Radiology

Interventional radiology uses image guidance to perform minimally invasive procedures that would otherwise require open surgery. Fluoroscopy, CT, and ultrasound guide the introduction of catheters, needles, and devices into vascular and non-vascular structures for diagnosis and treatment. Common procedures include angioplasty and stent placement for arterial occlusion, transcatheter arterial embolization for tumor blood supply interruption, percutaneous drainage of abscesses and fluid collections, and image-guided biopsy for tissue sampling. The American Board of Radiology overview of radiology specialties recognizes interventional radiology as a distinct primary certification path, reflecting its development from a diagnostic subspecialty into an independent procedural discipline. Advances in flat-panel fluoroscopy, cone-beam CT, and robotic-assisted catheter navigation continue to expand the complexity and precision of procedures that can be performed without general anesthesia or surgical incisions.

Radiation Oncology and Therapeutic Applications

Radiation oncology applies ionizing radiation to destroy or control malignant tumors. External beam radiation therapy uses linear accelerators to deliver precisely shaped radiation fields to tumor volumes while protecting adjacent normal tissue, guided by CT and MRI-based treatment planning. Techniques including intensity-modulated radiation therapy (IMRT), stereotactic body radiation therapy (SBRT), and proton therapy enable dose distributions that conform closely to tumor geometry. Brachytherapy places radioactive sources directly within or adjacent to a tumor, delivering high local dose with rapid dose fall-off. Nuclear medicine adds a therapeutic dimension through the use of radionuclides such as iodine-131 for thyroid cancer and lutetium-177-labeled peptides for neuroendocrine tumors. The IAEA nuclear medicine and diagnostic imaging resources coordinate standardized dosimetry protocols and promote access to these technologies in lower-resource settings.

Applications

Radiology has applications across a wide range of clinical and technical fields, including:

• Oncology, for tumor staging, treatment planning, and response assessment
• Emergency medicine, for rapid trauma evaluation and detection of acute conditions such as pulmonary embolism and stroke
• Cardiology, for coronary angiography, structural heart interventions, and cardiac imaging
• Gastroenterology, for image-guided endoscopy, hepatic intervention, and bowel evaluation
• Orthopedics and rheumatology, for fracture assessment, joint imaging, and monitoring of inflammatory disease